1. Field of the Invention
The present invention relates to a semiconductor light emitting device and a method of manufacturing the same, and more particularly, to a semiconductor light emitting device which can improve characteristics of the semiconductor light emitting device such as a forward voltage characteristic and a turn-on voltage characteristic, increase light emission efficiency by lowering an input voltage, and increase reliability of the semiconductor light emitting device by a low-voltage operation, and a method of manufacturing the same.
2. Description of the Related Art
In general, a semiconductor light emitting device is a device in which a semiconductor material emits light. An example of the semiconductor light emitting device includes a device such as a light emitting diode (LED) that emits light by electron-hole recombination occurring at a semiconductor junction.
The semiconductor light emitting device is being widely used for lighting, a display device and a light source. The semiconductor light emitting device can emit light of a desired wavelength even with low power and prevent generation of materials that are harmful to the environment, such as mercury. Thus, the development of the semiconductor light emitting device is being accelerated for energy saving and environmental protection.
Particularly, GaN-based LEDs have recently been developed and widely used. Also, the commercialization of mobile keypads, side viewers and camera flashes employing the GaN-based LEDs is leading to active development of general lighting using GaN-based LEDs. The GaN-based LEDs are required to act as light sources having characteristics that are demanded according to their application fields including backlight units of large-sized TVs, headlights of cars, general lamps, and even products for small-sized portable products implementing a large size, high output, high efficiency and high reliability.
When the GaN-based LEDs are manufactured, it is important to control characteristics such as contact resistance of an electrode formed on each semiconductor layer. Particularly, an n-type ohmic electrode contacting an n-type GaN-based semiconductor layer is required to implement a low forward voltage (Vf). Thus, the n-type ohmic electrode contacting the n-type GaN-based semiconductor layer needs to include a material having low contact resistance.
One of Ti, Cr, Ta, Al, Au and an alloy thereof is used for an n-type electrode to be formed on the n-type GaN semiconductor layer. However, a semiconductor light emitting device including the n-type electrode using general n-type electrode materials such as Ti, Cr, Ta, Al, Au and an alloy thereof has high contact resistance, which undesirably increases a forward voltage higher than a desired level.
Therefore, there is a need to develop an n-type electrode material that can increase light-emission efficiency and maintain reliability of a product by controlling a characteristic of a semiconductor light emitting device to a desired level.